1. Field of the Invention
The present invention relates to an apparatus and method for character recognition by recognizing user's writing motion using an acceleration sensor, which can be employed in various information electronic appliances.
2. Discussion of Related Art
In order to control the various electronic devices that have been developed, various user interface devices have been developed. In order to input text, keyboards or peripherals, such as a mouse, tablet, or touch screen, that sense motion in a two-dimensional space and convert the motion into text have been generally used. However, various other ideas have been suggested to perform control by sensing user's motion in three-dimensions.
Methods for sensing motion in three-dimensions can be classified into three types.
According to the first type of method, a moving object is photographed using cameras and the motion is analyzed by performing image processing of the photographs. Such a method has drawbacks in that a plurality of cameras are necessary, a user should use an object having a specific shape or color for the image processing, and the processing is complicated.
The second type of method uses the principle of triangulation. In such a method, a user device emits or reflects radio waves or sound waves and three or more receiving units record the time that the emitted/reflected radio waves/sound waves are received to triangulate the position of an object. Such a method also has drawbacks in that a plurality of transmission devices or reception devices should be arranged and precision is low.
Lastly, the third type of method involves attaching an inertial sensor to a user or a user device in order to directly detect motion. When employing such a method, three-axis translational motion and three-axis rotational motion should be sensed in order to determine the overall motion of an object in three-dimensions. Such translational motion and rotational motion can be sensed using inertial sensors like an acceleration sensor and a gyroscope sensor. According to such a method, slight motion can be sensed with relatively simple processing. However, there is a limit to miniaturization because an acceleration sensor and a gyroscope sensor should be used for three axes.
A method for character recognition according to the conventional techniques integrates acceleration twice, thereby calculating traces of motion. However, since sensing errors are accumulated in the integration process and results in a large difference of trace, it is very hard to compensate error for accurate recognition.
In addition, the conventional methods for sensing motion in three-dimensions have problems in distinguishing motion corresponding to a valid stroke among user motion from motion occurring between two strokes, thus causing difficulty in accurate recognition.